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Tuesday, October 9th, 2012
- Video: Watch the debate
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| 4:00a | Drawing a line, with carbon nanotubes  MIT chemists designed a new type of pencil lead consisting of carbon nanotubes, allowing them to draw carbon nanotube sensors onto sheets of paper. Photo: Jan Schnorr A new fabrication method created by MIT chemists — as simple as drawing a line on a sheet of paper — may overcome that obstacle. MIT postdoc Katherine Mirica has designed a new type of pencil lead in which graphite is replaced with a compressed powder of carbon nanotubes. The lead, which can be used with a regular mechanical pencil, can inscribe sensors on any paper surface. The sensor, described in the journal Angewandte Chemie, detects minute amounts of ammonia gas, an industrial hazard. Timothy Swager, the John D. MacArthur Professor of Chemistry and leader of the research team, says the sensors could be adapted to detect nearly any type of gas. “The beauty of this is we can start doing all sorts of chemically specific functionalized materials,” Swager says. “We think we can make sensors for almost anything that’s volatile.” Other authors of the paper are graduate student Jonathan Weis and postdocs Jan Schnorr and Birgit Esser. Pencil it in Carbon nanotubes are sheets of carbon atoms rolled into cylinders that allow electrons to flow without hindrance. Such materials have been shown to be effective sensors for many gases, which bind to the nanotubes and impede electron flow. However, creating these sensors requires dissolving nanotubes in a solvent such as dichlorobenzene, using a process that can be hazardous and unreliable. Swager and Mirica set out to create a solvent-free fabrication method based on paper. Inspired by pencils on her desk, Mirica had the idea to compress carbon nanotubes into a graphite-like material that could substitute for pencil lead. To create sensors using their pencil, the researchers draw a line of carbon nanotubes on a sheet of paper imprinted with small electrodes made of gold. They then apply an electrical current and measure the current as it flows through the carbon nanotube strip, which acts as a resistor. If the current is altered, it means gas has bound to the carbon nanotubes. Two major advantages of the technique are that it is inexpensive and the “pencil lead” is extremely stable, Swager says. “You can’t imagine a more stable formulation. The molecules are immobilized,” he says. The new sensor could prove useful for a variety of applications, says Zhenan Bao, an associate professor of chemical engineering at Stanford University. “I can already think of many ways this technique can be extended to build carbon nanotube devices,” says Bao, who was not part of the research team. “Compared to other typical techniques, such as spin coating, dip coating or inkjet printing, I am impressed with the good reproducibility of sensing response they were able to get.” Sensors for any gas In this study, the researchers focused on pure carbon nanotubes, but they are now working on tailoring the sensors to detect a wide range of gases. Selectivity can be altered by adding metal atoms to the nanotube walls, or by wrapping polymers or other materials around the tubes. One gas the researchers are particularly interested in is ethylene, which would be useful for monitoring the ripeness of fruit as it is shipped and stored. The team is also pursuing sensors for sulfur compounds, which might prove helpful for detecting natural gas leaks. The research was funded by the Army Research Office through MIT’s Institute for Soldier Nanotechnologies and a National Institutes of Health fellowship to Mirica. |
| 2:26p | Presidential campaigns offer energetic energy debate at MIT There could hardly be a more pressing issue than energy policy at a time of global warming, but it has rarely featured in this year’s presidential campaign. Until last Friday night at MIT, that is, when representatives of the Obama and Romney campaigns squared off in a crisp, serious-minded debate about energy, revealing significant differences between the candidates. At the event, hosted by the MIT Energy Initiative (MITEI), Oren Cass, policy director for Republican candidate Mitt Romney, summarized the challenger’s positions by noting that the former Massachusetts governor believes increased domestic fossil-fuel production should be a principal focus of energy policy. There has been a recent “energy revolution” in the techniques used to extract fossil fuels, Cass asserted, making “energy independence on this continent … a potential reality for the first time in decades.” The pressing issue, he said, is whether “we embrace the revolution that actually has occurred … or do we attempt to stifle it?” The Obama administration, Cass charged, has invested too heavily in promoting alternative energy, and has been insufficiently aggressive in backing fossil fuels: not opening up enough public lands and offshore waters for oil and gas drilling, and not yet approving the Keystone XL pipeline, which is intended to deliver oil to the United States from Canada. “The administration’s policies are misaligned with the goal of increased production,” Cass said. “When I think about what the American public wants, it’s to look for the kind of balanced approach the president is pursuing,” Aldy said, adding: “We’re going to use every tool we have available. Let’s not just focus on fossil fuels. We can do a lot in renewables, whether it’s for biofuels, wind or solar. We need to be creative in how we do this. We need to take advantage of opportunities [for] energy efficiency.” While domestic oil production is at a 14-year high, Aldy said, Obama has also signed new fuel-efficiency standards for the nation’s automotive fleet that will mandate an average of 54.5 mpg by the year 2025. Cass and Aldy also presented differing views on the government’s proper role in fostering energy innovation. Cass said that Romney supports ARPA-E, the federal government’s program to develop new clean-energy technologies, which was first funded with $400 million from the economic stimulus act that Obama signed in early 2009. However, Cass noted a few times, Romney would prefer to see the lion’s share of government backing for innovation go toward early stage basic research “Ultimately the biggest source of difference [between the campaigns] … is the question of what is the right way to promote innovation,” Cass said, adding that Romney believes in “government support in the very early stages of research, and reliance on the private sector to commercialize technologies to bring down their costs and to hopefully succeed in the market.” By contrast, Cass asserted, Obama has supported “massive subsidies for chosen industries ... which, in our judgment, has not been a success.” Aldy countered that the Obama administration has helped advance clean energy innovation through its ARPA-E grants, and created 250,000 jobs from the total of $90 billion spent on clean energy in the stimulus bill. “We need to continue to diversify … and continue to advance wind and solar,” he said, asserting that there is “a lot of job creation going on, it’s high-quality jobs in the manufacturing sector.” Let moderation be your guide The 90-minute debate, in front of a crowd of several hundred in MIT’s Kresge Auditorium, was moderated by Jason Pontin, editor-in-chief and publisher of Technology Review. The campaign representatives hewed closely to their time allowances throughout the debate, and Pontin permitted them a few unscheduled but concise rebuttals to address areas of particular disagreement. Four other journalists and three students from area universities offered questions as well at the forum, formally called the MITEI Presidential Energy Debate. In addition to debating energy production and innovation, the discussion also turned to the environmental effects of industrial production. One of the sharpest areas of disagreement pertained to the Environmental Protection Agency’s Mercury and Air Toxics Standards, issued in 2011, which regulate emissions from coal-fired powerplants. “The mercury standard makes incredible sense in terms of health,” Aldy said, mentioning the EPA’s estimate that the law will prevent 11,000 premature deaths per year. Cass underscored Romney’s opposition to it, arguing that the benefits did not equal the costs of the measure, including the “unemployment of a significant number of workers” at coal plants that could be shuttered on account of the measure. All told, the measure constitutes “one of the most outrageously unjustified regulations the country has ever seen,” Cass said. In his reply, Aldy described that characterization of the regulation as “shocking.” Cass also repeatedly criticized Obama for not being more direct about his position on so-called cap-and-trade legislation, among other matters. In response, Aldy noted that Obama “could not find any Republicans willing to work on a bill in the Senate in 2010” involving cap-and-trade, after the House of Representatives passed legislation for it in mid-2009. The two representatives did find common ground on a statement Aldy made early on in Friday evening’s proceedings: “There is a clear choice in this election.” |
| 3:00p | How cancer cells break free from tumors Although tumor metastasis causes about 90 percent of cancer deaths, the exact mechanism that allows cancer cells to spread from one part of the body to another is not well understood. One key question is how tumor cells detach from the structural elements that normally hold tissues in place, then reattach themselves in a new site. A new study from MIT cancer researchers reveals some of the cellular adhesion molecules that are critical to this process. The findings, published Oct. 9 in Nature Communications, offer potential new cancer drug targets, says Sangeeta Bhatia, the John and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science, and leader of the research team. “As cancer cells become more metastatic, there can be a loss of adhesion to normal tissue structures. Then, as they become more aggressive, they gain the ability to stick to, and grow on, molecules that are not normally found in healthy tissues but are found in sites of tumor metastases,” says Bhatia, who is also a member of the David H. Koch Institute for Integrative Cancer Research at MIT. “If we can prevent them from growing at these new sites, we may be able to interfere with metastatic disease.” Lead author of the paper is Nathan Reticker-Flynn, a PhD student in Bhatia’s lab. Other authors are former students David Braga Malta and Mary Xu, postdocs Monte Winslow and John Lamar, and research scientist Gregory Underhill. In addition, Richard Hynes, the D.K. Ludwig Professor of Biology and a member of the Koch Institute, and Tyler Jacks, director of the Koch Institute, are contributing authors on this study. Losing and gaining adhesion Cells inside the human body are usually tethered to a structural support system known as the extracellular matrix, which also helps regulate cellular behavior. Proteins called integrins, located on cell surfaces, form the anchors that hold the cells in place. When cancer cells metastasize, these anchors let go. In this study, the researchers compared the adhesion properties of four types of cancer cells, taken from mice genetically engineered to develop lung cancer: primary lung tumors that later metastasized, primary lung tumors that did not metastasize, metastatic tumors that migrated from the lungs to nearby lymph nodes, and metastatic tumors that travelled to more distant locations such as the liver. Building on a system they first described in 2005, the scientists developed technology allowing them to expose each type of cell to about 800 different pairs of molecules found in the extracellular matrix. After depositing cells onto a microscope slide in tiny spots — each containing two different extracellular matrix proteins — the researchers could measure how well cells from each tumor type bound to the protein pairs. The new technology is a huge step forward from current experimental methods for studying cellular adhesion, which are limited to much smaller numbers of cells and adhesion molecules, says Jan Pilch, an assistant professor at the University of Pittsburgh School of Medicine. “They’ve not only scaled this up dramatically, they’re able to study the adhesion proteins in combination, which allows them to identify adhesion synergies,” says Pilch, who was not part of the research team. The researchers were surprised to find that adhesion tendencies of metastatic cells from different primary tumors were much more similar to each other than to those of the primary tumor from which they originally came. One pair of extracellular matrix molecules that metastatic tumors stuck to especially well was fibronectin and galectin-3, both made of proteins that contain or bind to sugars. Although metastatic tumor cells share adhesion traits, they may take different pathways to get there, Reticker-Flynn says. Some tumor cells alter the combination of integrins that they express, while others vary the types of sugars found on their surfaces. All of these changes can result in higher or lower affinities for certain molecules found in the extracellular matrix of different tissues. In an analysis of human tumor samples, both primary and metastatic, the researchers saw similar patterns. Specifically, they found that the more aggressive the metastasis, the more galectin-3 was present. Previous studies have suggested that tumors pave the way for metastasis by secreting molecules that promote the development of environments hospitable to new cancer growth. Accumulation of galectin-3 and other molecules that help tumor cells colonize new sites may be part of this process, the researchers say. “There’s a lot of evidence to suggest that a hospitable niche for the tumor cells is being established prior to the cells even arriving and establishing a home there,” Reticker-Flynn says. Preventing cancer spread The findings offer potential new ways to block metastasis by focusing on a specific protein-protein or protein-sugar interaction, rather than a particular gene mutation, Reticker-Flynn says. “If those changes do confer a lot of metastatic potential, we can start thinking about how you target that interaction specifically,” he says. The researchers tested this approach by genetically knocking down the amount of an integrin found on the surface of cancer cells, which they had identified as interacting with fibronectin and galectin-3. In those mice, tumor spread was reduced. Other possible therapeutic approaches include blocking binding sites on fibronectin and galectin-3 with antibodies, so tumor cells can’t latch onto them. To help with efforts to develop such drugs, the research team is now trying to figure out the details of tumor cells’ interactions with galectin-3 and is developing new candidate therapeutics aimed at inhibiting those interactions. The research was funded by Stand Up to Cancer, the Koch Institute Circulating Tumor Cell Project, the Harvard Stem Cell Institute, the National Cancer Institute, the Howard Hughes Medical Institute and the Ludwig Center at MIT. |
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